Search Results

We present quantitative data on population size and plaza area in three groups of ancient Mesoamerican settlements: a sample of 30 Late Postclassic cities and towns from throughout Mesoamerica and two regional settlement systems from the Classic period, including south-central Veracruz (the Mixtequilla) and the Palenque region. Plaza size scales with population in a sublinear relationship in all three groups, meaning that larger settlements had considerably less plaza area per capita than smaller settlements. These results suggest that the currently popular interpretation drawn from Classic Maya archaeology that plazas were places designed to hold the entire urban population for passive viewing of spectacles may be incomplete. We argue that the observed quantitative relationships between population and plaza area support the notion that plazas were designed to be used for a variety of purposes—including several types of ceremonies and marketplaces—held at different times following a regular schedule.

The origin of the extraordinary strengthening of the highly alloyed austenitic stainless steel Sanicro 25 during cyclic loading at 700 °C was investigated by the use of advanced scanning transmission electron microscopy (STEM). Along with substantial change of the dislocation structure, nucleation of two distinct populations of nanoparticles was revealed. Fully coherent Cu-rich nanoparticles were observed to be homogeneously dispersed with high number density along with nanometer-sized incoherent NbC carbides precipitating on dislocations during cyclic loading. Probe-corrected high-angle annular dark-field STEM imaging was used to characterize the atomic structure of nanoparticles. Compositional analysis was conducted using both electron energy loss spectroscopy and high spatial resolution energy dispersive X-ray spectroscopy. High-temperature exposure-induced precipitation of spatially dense coherent Cu-rich nanoparticles and strain-induced nucleation of incoherent NbC nanoparticles leads to retardation of dislocation movement. The pinning effects and associated obstacles to the dislocation motion prevent recovery and formation of the localized low-energy cellular structures. As a consequence, the alloy exhibits remarkable cyclic hardening at elevated temperatures.